A wireless multihop network is a wireless network formed with multiple nodes where traffic (data traffic, control traffic, and so forth) from a source to a destination can traverse one or more intermediate nodes, with the traffic being transmitted over wireless links. Depending upon network configuration, special nodes (called portals) may exist in the wireless multihop network. Portals permit traffic flow in and out of the wireless multihop network, for example, a portal can connect disjoint wireless multihop networks, provide connectivity to wired networks, access to the Internet, and so on.
Information being carried in the traffic is typically formed into packets prior to transmission. Performance of a wireless multihop network, such as link throughput, in general, is limited by media access control (MAC) and physical (PHY) layer overhead that is associated with each packet. Packet overhead may include control and header information that is part of each packet as well as media contention time that contributes to a total time required for a packet to reach its destination. For example, in IEEE 802.11 wireless networks, packet overhead is a main source of throughput degradation.
A prior art technique used to reduce packet overhead is to combine multiple small packets into a large frame. The percentage of control and header information to actual data is lower for the large frame than for the multiple small packets. Furthermore, the media contention time is incurred only once in the transmission of the large frame instead of multiple times in the transmission of the multiple small packets that are contained in the large frame.
One disadvantage of the prior art is that for wireless links with relatively low quality, the probability of the successful transmission of a large frame is smaller than the probability of successfully transmitting multiple small packets. Therefore, if the transmission of a large frame fails, a retransmission will be required, which will increase the overall overhead of transmitting the data contained within the large frame. If the quality of the wireless links is particularly bad, the transmission of the large frame may never succeed and the wireless network can be flooded with retransmission attempts of the large frame to the point of potentially preventing the successful transmission of even small packets.
A second disadvantage of the prior art is that only single wireless links are taken into consideration when concatenating multiple packets into the large frame. If a source to destination path requires that multiple wireless links be traversed, the use of a single wireless link to determine a frame size can result in a frame size that is too large for reliable message transmission.